Maximal oxygen consumption (VO2max) during treadmill exercise has been performed in nearly 700 BLSA volunteers over the past 7 years. In a carefully selected nonobese group of 83 men and 101 women without exercise-induced ischemia, VO2max expressed in ml/kg body weight/min declined sharply with age (men: VO2max = 54.9-0.39 age, r2 = .60; women: VO2max = 41.0-0.25age, r2 = .50, both p less than .0001). After normalization for 24 hour urinary creatinine excretion, an index of total body muscle mass, the age decline in VO2max was markedly attenuated in both sexes (men: r2 = .14, women: r2 = .08). To determine the role of physical activity is preserving functional capacity with advancing age, we have measured VO2max, body composition, blood lipid, glucose tolerance, and cardiac volumes at rest, during maximal treadmill exercise in 19 highly trained men 60-76 years old. Whereas VO2max (51 plus/minus 1 versus 30 plus/minus 2 and HDL cholesterol (59 plus/minus 3 versus 49 plus/minus 3) were significantly higher than in age matched nonathletic controls, plasma LDL, fasting and 2 hour postcardial glucose were lower. Preliminary data during upright bicycle exercise suggest that both L ventricular end diastolic volume and stroke volume are greater and heart rate lower at any submaximal load than n control subjects. The metabolic effects of relatively prolonged submaximal treadmill exercise is being studied in normal BLSA men. Preliminary results suggest a significant age-related augmentation of plasma catecholamines after 45-60 minutes of exercise, similar to that previously found in BLSA men during short-term maximal treadmill testing. The response to maximal upright bicycle exercise in over 30 BLSA subjects with exercise- induced myocardial ischemia detect by ECG or thallium scan is being compared with that of age-related nonischemic BLSA controls. Gender differences in the hemodynamic response to bicycle exercise are also being explored.